Human disruption of coral reef trophic structure

Graham, Nicholas Anthony James and McClanahan, Tim R. and MacNeil, M. Aaron and Wilson, Shaun K. and Cinner, Joshua Eli and Huchery, Cindy and Holmes, Thomas H. (2017) Human disruption of coral reef trophic structure. Current Biology, 27 (2). pp. 231-236. ISSN 0960-9822

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The distribution of biomass among trophic levels provides a theoretical basis for understanding energy flow and the hierarchical structure of animal communities. In the absence of energy subsidies [1], bottom-heavy trophic pyramids are expected to predominate, based on energy transfer efficiency [2] and empirical evidence from multiple ecosystems [3]. However, the predicted pyramid of biomass distribution among trophic levels may be disrupted through trophic replacement by alternative organisms in the ecosystem, trophic cascades, and humans preferentially impacting specific trophic levels [4, 5 and 6]. Using empirical data spanning >250 coral reefs, we show how trophic pyramid shape varies given human-mediated gradients along two orders of magnitude in reef fish biomass. Mean trophic level of the assemblage increased modestly with decreasing biomass, contrary to predictions of fishing down the food web [7]. The mean trophic level pattern is explained by trophic replacement of herbivorous fish by sea urchins at low biomass and the accumulation of slow-growing, large-bodied, herbivorous fish at high biomass. Further, at high biomass, particularly where fishers are not selectively removing higher trophic level individuals, a concave trophic distribution emerges. The concave trophic distribution implies a more direct link between lower and upper trophic levels, which may confer greater energy efficiency. This trophic distribution emerges when community biomass exceeds ∼650 kg/ha, suggesting that fisheries for upper trophic level species will only be supported under lightly fished scenarios.

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Journal Article
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Current Biology
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This is the author’s version of a work that was accepted for publication in Current Cell Biology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Current Cell Biology, 27, (2) , 2017 DOI: 10.1016/j.cub.2016.10.062
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08 Dec 2016 15:02
Last Modified:
13 Aug 2020 04:53